Accessory module for implantable fluid dispensing device

ABSTRACT

An implantable fluid dispensing device has an accessory housing set into the biocompatible shape of its device canister. A shelf is set into the canister to accept the accessory housing which contains a filter, an externally accessible infusion septum, or other accessory. The function of accessories in the accessory housing is independently tested. After an accessory is selected to match the particular application, the accessory module is mounted on the canister.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to accessory modules designed for mountingon implantable fluid dispensing devices.

2. Background Art

A variety of fluid dispensing devices have attempted to more carefullyregulate diseases or pain in patients by delivering drugs to particularsites within the body. For example, it is believed that insulin deliveryby an implantable dispenser will regulate diabetes in a mannerimpossible through traditional injections.

These devices must be sealed to prevent migration of fluids between thepatient's body and the interior of the device. The common technique hasbeen to weld shut a metallic container, using technology similar to thatin heart pacemakers. This method of sealing a case is effective, but ispermanent and expensive to alter. Components within the case must beconsidered permanently encapsulated.

Particular applications of such fluid dispensing devices could beenhanced by having various accessories in combination with the permanentparts of the device, which reside within the case. For example, somedrug therapies are safer if the drug is filtered for either particles orbacteria. Because each drug and therapy has specific characteristics, itis expensive and impractical to design a variety of such filters as partof the permanent apparatus sealed within the case.

Another example of an accessory for the module is a port for infusion ofdrugs on an acute basis, to supplement the chronic administrationprovided by the fluid dispensing device. Attempts have been made to addexternal ports to be used in conjunction with such devices. For example,see the port disclosed in U.S. Pat. No. 4,360,031 to White, issued Nov.23, 1982. An external port is disclosed in U.S. Pat. No. 3,971,376 toWichterle issued July 27, 1976.

A means is needed to accommodate such drug-specific andapplication-specific devices other than permanently mounting them withinthe sealed case. Great manufacturing expense can be saved if accessorydevices can be added after the original manufacture. Better medicalflexibility could be achieved if doctors could specify particularaccessories to be added after manufacture.

SUMMARY OF THE INVENTION

The present invention provides an accessory module for mountingaccessories on an implantable fluid dispenser. A metallic case is sealedpermanently to include a fluid reservoir, means for pumping the fluid,and outlet means to pass fluid to the exterior of the case. The case hasa smooth biocompatible shape. It is generally curved to avoid irritationwithin the body. An indentation or shelf is set into this curvedsurface.

An accessory module, preferably of a biocompatible non-metallicmaterial, is shaped to fit in the indentation or shelf so that, when itis in place, an accessory housing of the module completes the curve ofthe case and presents to the patient a smooth complete curved surface,which does not cause irritation.

The accessory housing has a fluid inlet means for coupling to the fluidoutlet means on the case. It also has an accessory fluid outlet means topass fluid from the accessory housing out to the body of the patientthrough an attached catheter.

In one embodiment, the accessory housing includes a filter for filteringfluid as it passes from the accessory inlet to the accessory outlet.

In another embodiment, the accessory housing includes a port to allowfluid to be directed into the accessory housing and into the attachedcatheter from outside the patient's body. In one example, the port is aseptum for receiving a hypodermic needle. This allows direct injectionfrom outside the body of the patient of fluid which would pass throughthe housing outlet into a catheter into the patient's body withoutinterfacing with the sealed case.

A fluid dispensing device constructed according to the present inventionallows great savings of manufacture in that various accessories can beadded to the device after its manufacture. A doctor can specify aparticular type of filter, or a particular type of port, or otheraccessory to be added on to a fluid dispensing device after itsmanufacture. In one embodiment, such devices can be added by the doctorat the site of implantation.

By separating accessories from the sealed case, the accessories can beseparately tested. Testing filters, for example, within a sealed fluiddispensing device is extremely difficult. Filters can be separatelytested in the present invention and later added for use in the patient.

This invention solves the prior art problems of bulky or loose devicesadded to the fluid dispensing device. The device retains the same smoothbody-compatible curve to minimize irritation to tissue of the patient.The accessory devices are fixedly mounted on the sealed case in alocation where they may be easily located by the physician. The greatestpossible flexibility in combinations of accessory devices and economy isachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a fluid dispensing device with anaccessory module mounted;

FIG. 2 is an enlarged fragmentary side elevational view of oneembodiment of a first embodiment of the accessory module of FIG. 1;

FIG. 3 is a partially cross-sectional view, partially cut-away viewtaken on line 3--3 of FIG. 2;

FIG. 4 is a fragmentary enlarged view of a second embodiment of theaccessory module of FIG. 1;

FIG. 5 is a partially cross-sectional, partially cut-away view taken online 5--5 of FIG. 4;

FIG. 6 is an enlarged fragmentary view of a third embodiment of theaccessory module of FIG. 1;

FIG. 7 is a partially cross-sectional, partially cut-away view taken online 7--7 of FIG. 6;

FIG. 8 is an enlarged fragmentary cross-sectional view taken on line8--8 of FIG. 6;

FIG. 9 is an enlarged fragmentary cross-sectional view taken on line9--9 of FIG. 7; and

FIG. 10 is an enlarged fragmentary cross-sectional view taken on line10--10 of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An implantable drug dispenser 20 is illustrated having a smooth exteriorsurface which minimizes irritation on human tissue when implanted. Theparticular dispenser 20 illustrated is shaped like a short cylinder,similar to a hockey puck with rounded edges. Drug dispenser 20 isprovided with an inlet 22 for filling with a selected medication. In theexample illustrated, inlet 22 is a septum which is pierced with ahypodermic needle inserted through the patient's skin.

Drug dispenser 20 includes a sealed canister 24 and an accessory housing26. Canister 24 is preferably made of a biocompatible metal, such astitanium, which is welded to make a hermetically sealed enclosure forthe fluid reservoir and mechanics of the drug dispenser 20. Canister 24is provided with an indentation 28 which is set in from the normallysmooth shape of canister 24. In this case, indentation 28 is a shelf. Inother embodiments, indentation 28 is a section removed from the shape ofcanister 24. Accessory housing 26 is shaped to mount in shelf 28, sothat it blends into the smooth biocompatible outside curve of canister24.

Accessory housing 26 1s preferably made of biocompatible,drug-compatible material, such as an inert plastic like polypropylene.

An accessory fluid outlet 30 is mounted on accessory housing 26. Afluid-conveying catheter is mounted on accessory fluid outlet 30 at thetime of implantation.

In FIG. 1, accessory housing 26 is shown exploded away.

The enlarged fragmentary view of FIG. 2 shows a first embodiment of theaccessory module of FIG. 1 which includes a filter 32. Canister 24includes a fluid outlet 34 which mates with an accessory fluid inlet 36in accessory housing 26. Fluid passes out of a dispensing mechanism incanister 24 through canister fluid outlet 34, accessory fluid inlet 36and passage 38 into a filter chamber 40 in accessory housing 26. In theembodiment illustrated, filter chamber 40 is a generally rectangularopening. A filter membrane 42 is mounted within filter chamber 40.

In one embodiment of this embodiment, the filter membrane is ahydrophyllic 0.1 micron pore-size bacterial/pyrogen retentive membrane.This membrane is constructed of an inert polymer such as nylon or PVDFto ensure long-term stability. In another embodiment, this filtermembrane is a 50 micron pore-size membrane designed to filter largerparticles and emboli. In another version of this embodiment, the filtermembrane is partially hydrophyllic and partially hydrophobic to allowboth drug and small gas bubbles to be filtered and to prevent any airlock.

In the embodiment illustrated, filter membrane 42 is rectangular. Itextends across the entire filter chamber 40 so that fluid enteringthrough passage 38 passes along one entire side of filter membrane 42and must pass through membrane 42 to progress to passage 44, from whereit passes out of accessory flu1d outlet 30. In this manner, all drugdispensed by fluid dispenser 20 is filtered by filter membrane 42 beforebeing dispensed in the body of the patient.

Accessory housing 26 is mounted on canister shelf 28. A first mountingstud 46 on canister 24, protrudes into a first mounting hole 48 inaccessory housing 26.

First mounting stud 46 is provided with a fixation slot 50 therethrough.A fixation access opening 52 is provided in accessory housing 26 whichis open to first fixation slot 50. Once accessory housing 26 ispositioned on shelf 28 so that first mounting hole 48 accepts firstmounting stud 46, a fixation wedge 54 is inserted through first opening52 into first fixation slot 50, thereby locking accessory housing 26 inplace. In the illustrated embodiment, first opening 52 is then filledwith plastic or adhesive material to hold first fixation wedge 54 inplace.

Similarly, at an opposite end of accessory housing 26, a second mountingstud 56 on canister 24 is covered by a second mounting hole 58 inaccessory housing 26. Second mounting stud 56 has a second fixation slot60 therethrough. A second opening 62 in accessory housing 26 allowsaccess from outside the accessory housing 26 to second fixation slot 60.A second fixation wedge 64 is inserted through second opening 62 intosecond fixation slot 60 to lock canister 26 to second mounting stud 56.

Accessory housing 26 is provided with an additional filling inletopening 66. In the embodiment illustrated, the device 20 is pressurizedwith a constant pressure fluid through filling inlet 67. After thedevice is filled through inlet 67, the inlet 67 is permanently sealed.The inlet 67 projects slightly outside the canister 24. This inlet isaccepted into inlet opening 66 as canister shelf 28 receives accessoryhousing 26.

The illustrated accessory housing is easily applied to canister 24 atany point after manufacture. The filter in the embodiment illustrated inFIG. 2 can be installed in the plastic housing 26 and fully testedwithout interacting in any way with the mechanisms in canister 24. Whenthe time for final assembly arrives, whether it be at the factory or ina hospital setting, a housing 26 containing the appropriate filtermembrane 42 is selected and mounted on first and second mounting pins 46and 56.

A second embodiment of an accessory housing is illustrated in FIGS. 4and 5. Accessory housing 80 mounts on first and second mounting pins 46and 56 in a manner identical to the embodiment illustrated in FIGS. 2and 3. In this embodiment, accessory fluid inlet 82 includes a checkvalve 84 to prevent back-flow of fluid from accessory housing 80 intocanister fluid outlet 34. Fluid received through accessory fluid inlet82 passes through first passage 86 into a septum chamber 88 located inaccessory housing 80. From septum chamber 88, fluid passes throughsecond passage 90 and out through accessory fluid outlet 92 into thepatient. Septum chamber 88 is accessible from outside of accessoryhousing 26 through piercible septum 94. This septum 94 operates in amanner similar to inlet 22 in canister 24. A hypodermic needle fromoutside the patient is inserted through the skin and through septum 94into chamber 88. Fluid is then injected into chamber 88. Check valve 84prevents back flow into canister 24. This fluid immediately passesthrough second passage 90 and out accessory outlet 92.

In this manner, acute dosages of drug or diagnostic fluids are injectedinto the patient without employing the pumping apparatus of canister 24.The accessory housing 80 is fixedly mounted on canister 24 and providesa smooth contour continuing the lines of canister 24. This fits wellwithin the patient and prevents aggravation of surrounding tissue, yetprovides additional acute drug access through septum 94. The prior arttechniques of sharp or irregular projections from the device areavoided.

A third embodiment of the present invention is illustrated in FIGS. 6and 7. This embodiment includes an accessory housing 100 provided with afilter chamber 102 and filter member 104 which operate in the manner ofthe embodiment illustrated in FIG. 2. Fluid is accepted throughaccessory fluid inlet 106, passes through first passage 108 and intofilter chamber 102. After fluid passes through filter membrane 104 itproceeds through second passage 110. In second passage 110 is a checkvalve 112, shown in schematic form, which allows fluid to pass only inone direction. Second passage 110 opens into septum chamber 114. Chamber114 is subsequently open to third passage 116 which empties intoaccessory outlet 118.

As in the embodiment illustrated in FIGS. 4 and 5, a septum 120 allowsaccess by a hypodermic needle to septum chamber 114. Acute infusions offluid may be injected by a hypodermic needle into chamber 114 as in theearlier described embodiments. Check valve 112 prevents the acuteinfusion of fluid from proceeding backward into filter chamber 102 orcanister 24.

In this embodiment, accessory housing 100 mounts on shelf 24 in a manneridentical to earlier illustrated embodiments.

With the present invention, various combinations of external accessoriescan be easily added to an infusion device to tailor the device to theneed of the particular patient. As illustrated, a filter, an infusionseptum, combination thereof, or other accessory can be installed in thismanner without requiring complex factory installation. The preferredembodiment of accessory module can easily be fabricated, such as bymolding, from a biocompatible polymer such as polypropylene or afluoropolymer at little expense. The accessories in the accessoryhousing can be independently tested without interfacing with thecomplexities of the apparatus within the infusion pump canister. Ifthere are failures in tested devices, they can be discarded at low costwithout involving the great expense of scrapping or repairing the sealedcase.

The correct accessory for the type of drug to be adminstered is selectedand mounted on the canister as needed. In some preferred embodiments,the accessory housing is mounted by the physician after selection of theproper accessories. Specific filters can be stocked for specific drugsor therapies. This increases the likelihood that the proper device willbe available in a timely manner when needed by a patient for whom hasbeen prescribed a particular therapy. The choice can be made for eachpatient whether to include a filter, an infusion port, or a combinationof accessories. This greatly increases the flexibility of the device, inthat the doctor can alter characteristics of the device by choosingproper accessories designed to maximize treatment for the patient.

When new drug therapies are discovered which require differentaccessories, the accessories can be manufactured and tested withoutexpensive redesign of components within the hermetically sealed case.

While the present invention has been illustrated in terms of particularembodiments, it should be noted that the invention may take the form ofother useful embodiments not illustrated herein.

What is claimed is:
 1. An implantable fluid dispensing devicecomprising:a sealed case having a smooth biocompatible curved surface;the case having an indentation inwardly diverging from the curvedsurface; and an accessory housing shaped to mount on the case in theindentation and shaped to conform generally to the curved surface. 2.The device of cla1m 1 further comprising:fluid outlet means in the casefor passing fluid from inside the case to outside the case; fluid inletmeans in the accessory housing for coupling to the fluid outlet means onthe case when the housing is mounted on the case; and second fluidoutlet means on the accessory housing for passing fluid from within theaccessory housing into a patient's body.
 3. The device of claim 2further comprising filter means mounted in the accessory housing forfiltering the fluid as it passes from the inlet means to the secondoutlet means.
 4. The device of claim 2 further comprising:port means onthe accessory housing for receiving fluid to be passed through theaccessory housing and out the second outlet means.
 5. The device ofclaim 4 wherein the port means includes a pierceable septum forreceiving fluid from a hypodermic needle inserted through skin of thepatient.
 6. An implantable fluid dispensing device comprising:a sealedcase having a fluid storage reservoir; fluid outlet means on the casefor passing fluid from the reservoir to the exterior of the case; thecase having a curved shape and having a shelf stepped in from the curvedshape; an accessory housing shaped to mount in the shelf and to conformgenerally to the external curved surface; accessory fluid inlet means inthe accessory housing for coupling to the fluid outlet means on the caseand for passing fluid into the accessory housing; filter outlet means inthe accessory housing for passing fluid from the accessory housing intoa patient's body; and filter means mounted in the accessory housing forfiltering fluid passing from the accessory fluid inlet to the accessoryfluid outlet.
 7. The device of claim 6 further comprising an inlet portin the accessory housing for receiving fluid from outside the patient'sbody.
 8. The device of claim 7 wherein the inlet port includes a septumfor receiving a hypodermic needle.
 9. An implantable fluid dispensingdevice comprising:a sealed case having a fluid storage reservoir; fluidoutlet means on the case for passing fluid from the reservoir to theexterior of the case; the case being shaped with a biocompatible curvedperimeter and having a shelf stepped in from the curved perimeter; anaccessory housing mounted on the shelf and shaped to conform to thecurved perimeter; an inlet port mounted on the accessory housing forinjecting fluid into the housing; and valve means for preventing fluidfrom the housing from passing into the sealed case.
 10. The device ofclaim 9 further comprising filter means mounted in the accessory housingfor filtering fluid as it passes through the accessory housing.
 11. Anaccessory module for mounting on an implantable fluid dispensing devicecomprising:an accessory housing formed of inert biocompatible plastichaving one curved side shaped to contact the interior of the body in anon-irritating manner and a second side shaped to be inset in its fluiddispensing case; accessory fluid inlet means mounted on the accessoryhousing for receiving fluid; accessory outlet means mounted on thehousing for dispensing fluid; and an accessory mounted within thehousing for processing fluid.
 12. The device of claim 11 wherein theaccessory is a filter for filtering fluid as it passes through thehousing.
 13. The device of claim 11 wherein the accessory is a port forreceiving fluid from a source external to a patient's body and a valvefor preventing flow of fluid out of the accessory inlet port.